Characterization and catalytic activity of covalently linked bipyridyl ruthenium OXO dimers

This paper reports that covalently linked bipyridyl ligands (L-L) with alkyl linkages varying from (-CH[sub 2]-)[sub 2] to (-CH[sub 2]-)[sub 12] were used to prepare ruthenium oxo dimers of the form [bpy (H[sub 2]O)RuO(L-L)Ru(H[sub 2]O) (bpy)][sup 4+]. The bridging alkyl linkage increased the stability of these oxo dimers by maintaining the relative proximity of the two ruthenium centers even when the oxo bridge is cleaved. These complexes have been characterized by electronic spectroscopy and electrochemistry. The electrochemistry in CH[sub 3]CN/0.1M TBAP exhibits a reversible one-electron oxidation followed by a second reversible two-electron oxidation which becomes catalytic in aqueous solution. The catalytic generation of dioxygen from water was observed upon bulk electrolysis of the oxo dimer at + 1.39 V.